In the following text laser head means a device comprising essentially an active material and means for exciting this active material. A laser head amplifies when a laser beam passes through its active material. Further, a laser generator may be obtained by adding a resonant optical cavity to such a head. Lastly, when a laser head or a succession of laser heads is disposed at the output of a laser generator, a laser generator device is obtained.
A laser amplifier head is known in which the active material is constituted by a neodymium-doped glass rod and the excitation means comprise light discharge tubes disposed around the side surface of the rod. When a high energy laser beam passes through the active material, the cross-section of the rod must be large. But with a large rod it is observed that the light energy generated by the discharge in the tubes provokes a non-homogeneous illumination of the rod. An axial zone of the rod is less illuminated and the population inversion therein is smaller. This results in a deformation of the cross-section of intensity of the amplified laser beam and an appreciable reduction of the power of this beam.
To remedy these drawbacks, laser head disc structures have been produced in which the light excitation is directed mainly onto the surfaces of the discs, but these structures have a low excitation efficiency and are also technically very difficult to produce. "Plate" structures have also been proposed in which the active material is excited by discharge tubes disposed along one surface of the plate. In some cases, plate structures make it possible to improve the homogeneity of the illumination of the active material, but have the disadvantage of being difficult to produce because generally it is necessary to treat the surface of the plate which is illuminated by the discharge tubes, in order to improve the penetration of the light radiation in the plate and the reflection of the laser beam on this surface; this treatment withstands poorly the power of the radiation of the discharge tubes.
The present invention provides means for increasing the excitation of a laser head and in preferred embodiments it is used to mitigate the disadvantages of known laser heads referred to above and to provide new high-power laser head structures in which the active material is excited more homogeneously.